![]() The current GPS availability for nonprecision approaches in the continental United States is more than 99.99 percent, meaning on average, if you check RAIM 10,000 times, you’ll fail to get RAIM only once!īut don’t be surprised if there’s insufficient signal quality to fly to LPV minimums. Incidentally, if you do a RAIM check and it fails, you may want to play the lottery. But RAIM can’t tell you if you’ll have sufficient signal quality to fly to LPV minimums, so there’s no need to check it if you plan to fly to LPV approach or LNAV/VNAV minimums. If flying in oceanic or remote areas, the FAA requires that you run an FDE prediction program, available from Garmin and other companies, to check GPS satellite coverage.Įn route, you can check RAIM if you’re planning to fly to LNAV minimums. You’ll also want to contact Flight Service for any WAAS notams. Your preparation before leaving the ground should include checking that your GPS database and charts are current - and if your charts are on an iPad, checking that the iPad is fully charged. Circling minimums permit you to circle to land on any runway, except those prohibited in the chart notes.įlying an approach to LPV minimums starts long before you reach the approach. ![]() They are the only straight-in GPS minimums that can be flown with a non-WAAS, approach-certified GPS. LNAV, or lateral navigation, mini-mums are used to fly a series of stair steps until you reach a minimum descent altitude (MDA). LP, or localizer performance, minimums are like a localizer approach the angular guidance narrows as you near the runway and there’s no vertical guidance. You can usually ignore the LNAV/VNAV minimums, since LPV minimums are almost always lower. Other minimum choices may include LNAV/VNAV, LP, LNAV and circling. LPV approach minimums, usually 200 or 250 feet agl, are typically the lowest available on a GPS approach. LPV stands for “localizer performance with vertical guidance,” meaning it’s similar in precision to the localizer and glideslope of an ILS approach. Technically there is no such thing as an “LPV approach.” Instead, LPV approach is just one of several minimum types that can be flown on a GPS approach with a WAAS-capable, instrument-certified GPS. So I did much of what you’ll read here comes from my Max Trescott’s GPS and WAAS Instrument Flying Handbook. That said, flying a GPS approach can be so complicated you could write a book about it. So flying a GPS approach to LPV minimums can be as simple as flying an ILS approach, but only if you’re extremely familiar with the GPS in your cockpit. Of course each GPS is different and the odds of successfully loading an approach on an unfamiliar GPS are slim. If you know how to operate a particular GPS model and can successfully load a GPS approach, flying an approach to LPV minimums can be as simple as flying an ILS approach. By dialing in the right frequency and keeping the needles centered, a pilot could successfully fly an approach even using radios he or she had never seen before. In the past, pilots had it easy when flying an ILS (instrument landing system) approach. On this approach, you can descend to as low as 860' MSL until you see the runway, or until you reach the MAP.One challenge for instrument pilots is that the rapid change in technology found elsewhere in our lives has invaded the cockpit. LNAV stands for Lateral Navigation, and MDA as you now know, stands for Minimum Descent Altitude. Looking at the example below, the RNAV (GPS) RWY 34 at Newport Municipal, you'll see that under the minimums section there the words "LNAV MDA" are written. Under the minimums, you will see different lines of minimums you can fly (this will depend on the type of equipment you have onboard) and whether they correspond to a Decision Altitude or a Minimum Descent Altitude. To find MDA or DA, you'll look to the Minimums section toward the bottom of the chart. Now that you know the theory behind MDAs and DAs let's identify them on approach charts. But if the weather is at minimums, it's entirely likely that you'll be making your continue/go-around decision at DA. In practical terms, you typically descend out of the clouds and have good enough visibility to see your landing runway well before you reach DA. Here's how it works: as you descend down the electronic glideslope of an approach, as you reach DA, you look up, determine if you have the three requirements to land, and then make your decision, which is either 1) continue your descent down the glidepath and land, or 2) go missed and start climbing.
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